Techniques for acquiring data regarding hemoglobin of an organism by use of near-infrared light have been well known (in general, such techniques are collectively called “near-infrared spectroscopy (NIRS)”).
One example application thereof is an oxymeter, which has been widely used. In recent years, functional imaging for noninvasively detecting cerebral function through detection of a change in the cerebral circulation blood flow has been widely noticed. This technique has been widely used in, for example, positron emission tomography (PET), which utilizes water labeled with O15, and in a magnetic resonance imaging (BOLD-fMRI) which utilizes the magnetic susceptibility effect of deoxy hemoglobin. Development of a functional imaging technique (called optical CT) which utilizes near-infrared light has been pursued, because such functional imaging enables obtainment of hemoglobin information by use of near-infrared light. However, this functional imaging technique cannot be said to have been established.
Diagnostic apparatuses and tools can be divided into the following three categories.
(1) A large apparatus such as those used in connection with the above-mentioned PET and MRI, which requires a patient to go to a place where the apparatus is installed in order to receive an examination.
(2) A small apparatus, such as an electrocardiograph, an electroencephalograph, or an oxymeter, which is disposed at a bedside or in an ambulance, or a portable apparatus which is transported to the location of a patient.
(3) An instrument, such as a stethoscope, which a medical worker always carries on his person.